Preparation of iron and nickel carbonyls



United States Patent 3,112,179 PREPARATION OF IRQN AND NICKEL CARBGNYLS Arnold F. Schrneckenbecher, Poughkeepsie, N .Y., assignor to General Aniline & Fiim Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. 30, 1969, Ser. No. 72,573 4 Claims. ill. 232.t)3)

This invention relates to an improved process for preparation of iron and nickel carbonyls.

In producing iron and nickel carbonyls by reaction of carbon monoxide with compositions containing the finely divided metals, the rate of conversion tends to vary over a wide range, and constitutes a major factor in determining the cost of the product. Use of carbon monoxide under high pressure and maintenance of relatively high temperatures favor an increased rate of conversion, but the rate still remains dependent on the nature and composition of the metal-bearing materials subjected to carbonylation.

Sulfides, and sulfur compounds which are converted to sulfides in the course of the treatment, are known to enhance the carbonylation rate of nickel, and nickel mattes which contain nickel sulfide have been used to advantage in the production of nickel carbonyl. In one procedure, nickel matte is fused with finely divided iron or copper whereby the latter are converted to sulfides, liberating metallic nickel and yielding a product having a relatively high carbonylation rate. In another procedure, pulverized nickel matte is mixed with copper and iron and treated with sulfuric acid whereby reactivity of the composition toward carbon monoxide is enhanced. In a procedure for converting iron ore to iron carbonyl, the

ore was pre-treated with nickel sulfate, which upon reduc tion yields nickel sulfide, substantially promoting the rate of conversion of iron to iron carbonyl.

Other procedures heretofore employed involve conversion of nickel and iron ores to the oxides, followed by reduction to yield the metals in finely divided form in which they are suitable for carbonylation. However, the carbonylation rate is relatively unsatisfactory unless sulfidcs or sulfur compounds are present initially in the raw materials or added in a special pre-treatment step. Thus, in order to take advantage of known means for enhancing the carbonylation rate of iron and nickel, it was necessary heretofore to select specific sulfur-containing raw materials or to subject such materials to pro-treatments in order to incorporate sulfur in appropriate form therein.

it is an object of this invention to provide a method for preparing nickel and iron carbonyls at an unusually high reaction rate from raw materials containing the metals, but without the necessity of including or incorporating sulfides or other sulfur compounds.

In accordance with my invention, nickel containing ores or other raw materials are converted by means of known processes to pulverulent nickel oxide. The latter is mixed with sponge iron (which serves as a binder) in an amount ranging from to 98% by weight of the mixture, and the latter is then compacted under high pressure to form pellets. These are subjected to reduction by heating in a stream of gaseous hydrogen, and the reduced pellets are then heated in carbon monoxide under high pressure to convert the iron and nickel, formed in the reduction, to the corresponding carbonyls. The latter can be recovered by condensation from the exit gases, and separated, if desired, by fractional distillation into the component carbonyls.

It has been found that the carbonylation rate for nickel and iron in the process of tlns invention is approximately 30 to 60% higher than for similarly pelleted 35,112,179 Patented Nov. 26, 1963 sponge iron alone, or similarly pelleted nickel oxide containing only minor amounts of inert metallic binders.

My invention will be more fully understood from the following examples wherein parts and percentages are by weight, unless otherwise indicated.

Example 1 parts of sponge iron having an average particle size of about 0.84 mm. (20 mesh) prepared by heating magnetite at reduction temperature in a stream of hydrogen gas, were thoroughly mixed with 20 parts of technical grade green nickel oxide (NiO) of a fineness adapted to pass a 200 mesh screen, and the mixture was pressed into cylindrical pellets about /2 inch high and 78 inch in diameter, using a pressure of about 8.4 tons per square inch. 300 grams of the pellets were placed in a vertical tube 3 inches in diameter and 2 feet long, equipped with a heating jacket, and heated therein for 24 hours at 400 C. while passing a stream of gaseous hydrogen through the tube at atmospheric pressure. The temperature was then reduced to 100 C., and carbon monoxide was passed through the pelleted mass at a pressure of 960 lbs. per square inch (gauge) at a rate of 1 liter per minute. The gas leaving the pelleted mass was passed through a trap cooled at about 25 C. to 15 C. in which metal carbonyls were condensed. The latter were removed through a valve at the base of the trap at hourly intervals. At the end of 7 hours, the quantity of carbonyls recovered indicated that 70.6% of the nickel-iron content of the pellets had been converted during said period to Ni(CO) and Fe(CO) Example 2 3 batches of pellets were prepared as described in Example 1 from the same components, but employing other.

Percentage conversion to carbonyl in 7 hours Weight ratio, NiO/Fe:

For purposes of comparison, 3 additional batches of pellets were prepared as described in Example 1, but using for the first batch sponge iron alone, for the secondnickel oxide containing 1% of copper powder as a binder and for the thirdnickel oxide containing 5% aluminum powder as a binder (copper and aluminum powders are substantially inert in the carbonylation, and were added to provide requisite pellet strength for the nickel oxide). The 3 batches of pellets were subjected to reduction and carbonylation in the manner described in Example 1 and the percentage conversion to carbonyl was measured in each case at the end of 7 hours. The results were as follows.

Percentage conversion to Pelleted materials: carbonyl in 7110\115 100% sponge iron 42.0 99% MO, 1% Cu powder 43.5 Ni(), 5% Al powder 46.2

range.

3 oxide containing minor amounts of substantially inert metallic binders.

The nickel oxide powder employed in the process of the invention is ordinarily obtained from nickel ores in which the nickel occurs as a sulfide, arsenide or hydrated silicate. In the case of sulfideores, the nickel sulfide, remaining after separation of copper and iron compounds, is roasted in air yielding pulverulent nickel oxide suitable for use in the process of this invention. Arsenide ores usually contain iron as well as. arsenic in addition to nickel, and are roasted in air, with or without chlorine or other supplementary oxidizing agent. Nickel oxide powder resulting from this treatment is also suitable for use in the present process. Hydrated silicate ores are usually fused with caustic soda and sodium nitrate, the nickel converted to a sulfide, and the sulfide converted by roasting to pulverulent nickel oxide. Similarly nickel oxide obtained by heating nickel carbonate or nickel hydroxide precipitated from solutions of nickel salts by reaction with alkaline carbonates or hydroxides is also suitable. The nickel oxide ordinarily employed is NiO but Ni O can be used instead, since both are converted to nickel in the reduction treatment. If larger particles, lumps or aggregates of nickel oxide remain, the product is ground to a powder in which the nickel oxide is preferably fine enough to pass a 100-200 mesh screen.

The sponge iron employed in the process of the invention is produced by reducing an iron oxide such as magnetite in a stream of hydrogen at an elevated temperature e.g. 300400 C., at which the iron does not sinter. The resulting product consists of spongy agglomerates having an average particle size adapted to pass a 20 mesh screen i.e. an'average particle diameter of about 0.84 mm.

The sponge iron and nickel oxide powder are thoroughly mixed in a Weight ratio ranging from 98:2 to 50:50, and the resulting mixture is pelleted under a pressure of at least 5 tons per square inch. Pressures as high as 16 tons per square inch can be used but ordinarily 8 to 10 tons per square inch are preferred to insure production of shaped pieces or pellets which resist crumbling during the subsequent reduction and carbonylation treatments. At least 50% by weight of sponge iron should be present in the mixture in order to produce compacted pellets of sufficient strength to withstand crumbling in the subsequent treatment steps. A minimum of 2% by weight of nickel oxide should be present to provide the accelerated carbonylation rate of the present invention.

The term pellet as employed herein is used in a general sense to refer to shaped pieces having a form adapted to maintain space between them for passage .of gas when charged in random fashion in a reaction vessel, i.e. pieces so shaped as to avoid a tendency to regular stacking or nesting. Thus the pellets may be spherical, ovoid, bri- .quette-shaped or pillow-shaped, oras employed in the foregoing examples-in the shape of cylindrical plugs.

The size of the pellets may vary over a considerable Thus, granules having an average diameter as small as 0.84 mm. mesh) can be employed, although the reaction rate is somewhat reduced as compared with pellets having the dimensions indicated in the examples. The size may also range up to 3 inches average diameter but in this case the reaction rate tends to decrease because of the reduced surface area of a given weight of product. It is therefore preferred to use pellets of such size that the average diameter is from 0.5 to 1.0 inch as illustrated in the preceding examples.

Reduction is carried out by charging the pellets into a reaction vesseladvantageously of tubular form and passing a current of hydrogen through the mass by heating at a temperature from 300 to 700 C. While superatmospheric pressures are effective, atmospheric pressure sufiices. Completion of the reduction may be detected '4 by observing disappearance of moisture in the hydrogen stream leaving the reduction chamber.

If desired, the carbonylation treatment may be carried out in the same reaction vessel employed for the reduction treatment, if the reaction vessel is constructed to withstand the relatively high pressures employed. Super-atmospheric pressure is used in order to permit use of elevated temperatures, at which the reaction rate is greatly increased. At atmospheric pressure the temperature must be limited to 40 C., since higher temperatures cause decomposition of nickel carbonyl. By increasing the carbon monoxide pressure, the carbonyl decomposition temperature is raised, and at these temperatures, carbonylation proceeds at a much higher rate. Thus, at a CO pressure of 200 atmospheres (about 2900 lbs. per square inch), the carbonylation temperature can be raised to 170 C. while at a CO pressure of 900 lbs. per square inch (gauge) employed in the examples, a temperature of C. is suitable. In general, the carbonylation temperature should be selected within the range of 70 to C., and the CO pressure maintained high enough within the range of 500 to 3000 lbs. per square inch (gauge) to prevent decomposition of nickel carbonyl.

A stream of carbon monoxide is passed at the selected temperature and pressure over the reduced pellets, and the nickel tetra-carbonyl and accompanying iron pentacarbonyl are condensed from the exit gases by cooling Residual carbon monoxide can then be re-circulated to the carbonylation chamber. The nickel and iron carbonyls collected as products can be separated in known manner by fractional distillation.

Variations and modifications which will be "obvious to those skilled in the art can be made in the procedure described and illustrated in the foregoing examples without departing from the spirit or scope of the invention.

I claim:

1. A process for preparing metal carbonyls, which comprises mixing nickel oxide powder with sponge iron of such fineness as to pass a 20 mesh screen, in such proportions as to yield a substantially uniform mixture consisting essentially of 50 to 98% by weight of sponge iron and 50 to 2% by weight of nickel oxide powder, forming compact pellets of said mixture ranging from 0.84 mm. to 3 inches in diameter at a pressure ranging from 5 to 16 tons per square inch, reducing the nickel oxide in said pellets by heating at 300 to 700 C. in a stream of hydrogen, passing a stream of carbon monoxide through a mass of the reduced pellets at a temperature of 70 to 170 C. while maintaining the carbon monoxide pressure at a sufficiently high level to prevent substantial decomposition of nickel carbonyl, and separating nickel and iron carbonyls from the resulting gaseous mixture.

2. A process as defined in claim 1 wherein said pellets are formed under pressures ranging from 8 to 10 tons per square inch and in shapes having an average diameter of /2 to 1 inch.

3. A process as defined in claim 2 wherein said reduction is carried out at a temperature of 300 to 700 C., and carbonylation is elfected at a carbon monoxide pressure of 500 to 3,000 lbs. per square inch.

4. A process as defined in claim 3 wherein said pellets are formed under a pressure of 8l0 tons per square inch,

said reduction is carried out at about 500 C. and car- References Cited in the file of this patent UNITED STATES PATENTS Simpson Aug. 20, 1940 Lewis et a1. July 31, 1956 

1. A PROCESS FOR PREPARING METAL CARBONYLS, WHICH COMPRISES MIXING NICKEL OXIDE POWDER WITH SPONGE IRON OF SUCH FINENESS AS TO PASS A 20 MESH SCREEN, IN SUCH PROPORTIONS AS TO YIELD A SUBSTANTIALLY UNIFORM MIXTURE CONSISTING ESSENTIALLY OF 50 TO 98% BY WEIGHT OF SPONGE IRON AND 50 TO 2% BY WEIGHT OF NICKEL OXIDE POWDER, FORMING COMPACT PELLETS OF SAID MIXTURE RANGING FROM 0.84 MM. TO 3 INCHES IN DIAMETER AT A PRESSURE RANGING FROM 5 TO 16 TONS PER SQUARE INCH, REDUCING THE NICKEL OXIDE IN SAID PELLETS BY HEATING AT 300 TO 700*C.IN A STREAM OF HYDROGEN, PASSING A STREAM OF CARBON MONOXIDE THROUGH A MASS OF THE REDUCED PELLETS AT A TEMPERATURE OF 70 TO 170* C. WHILE MAINTAINING THE CARBON MONOXIDE PRESSURE AT A SUFFICIENTLY HIGH LEVEL TO PREVENT SUBSTANTIAL DECOMPOSITION OF NICKEL CARBONYL, AND SEPARATING NICKEL AND IRON CARBONYLS FROM THE RESULTING GASEOUS MIXTURE. 